Two-year life history of the neolitsea leaf gall midge, Pseudasphondylia neolitseae Yukawa (Diptera, Cecidomyiidae)

The neolitsea leaf gall midge, Pseudasphondylia neolitseae is normally univoltine. In addition to the one-year cycle individuals, those with the two-year life history, in which the first-stage larvae enter prolonged diapause, were detected in recent years at various localities in southwestern Japan. The ratio of the two-year cycle individuals in a population varied from year to year and at different localities. A detailed two-year life history is described with special reference to the attack of two parasitoid species in relation to the developmental stages of midge larvae and of their leaf galls. The existence of the two-year cycle individuals in the midge population can be explained by the advantages derived mainly from diversifying risks against parasitoids and partly from escaping endoparasitism by entering prolonged diapause.